conservation of angular momentum
18 August 2006
KungfuHamster had a question from a youngling
some tyme ago...he is Sec3 btw!
"Does the Earth rotate because of gravity?"
gosh!! Basic Sec 1 Geography!!
No. The balance of gravitational forces causes the planets
to orbit the sun and the moon to orbit the Earth.
feelin beaten so quickly..
he asked another question...not of Sec1 standard!
"Then why does the Earth rotate?"
The Earth rotates because the Earth...
..err...was rotating when it was made...(how lame!)
It has continued rotating because
there is no friction in the vaccum of space...
feeling annoyed at how Kungfuhamster
answers so quickly..
he then another question...
"So why did the Earth rotate when it was made?"
Uhmmm... need to go for Chem. mock test
I'll tell you tomorrow...
the youngling laughed as Kungfuhamster walked off!!
He thinks i cannot answer his question...
he thinks he have
beaten me by the 3rd question..
wait wait i show him...my KungfuXaolin showdown!!
That sparked off a furious round of research.
Kungfuhamster knows it has something to do with
" the Conservation of Angular Momentum "
So it was off to google.com about angular momentum.
This is what Kungfuhamster found:
The angular momentum of a particle of mass 'M'
with respect to a chosen origin is given by
or more formally by the vector product...
The direction is given by the right hand rule
which would give L the direction out of the diagram.
For an orbit, angular momentum is conserved,
and this leads to one of Kepler's laws.
For a circular orbit, angular momentum doesn't apply!
How would a Sec3 understand this higher order thinking?
so what i found was Not very helpful.
Kungfuhamster started to develop
neurohaemorraging. [ my ang moh pro sia :) ]
So Kungfuhamster approached
the scientific specialist Jedi Masters..
"What is angular momentum?"
2 didn't know, 1 knows but can't recall (yeah right...)
1 made Kungfuhamster even more confused..SIGH
So kungfuhamster approached
the NON-scientific specialist Jedi Masters.
All of them stared at Kungfuhamster
like he was wearing his underwear on his head. [ LAME ]
Finally, one wise Jedi Master explained it:
' Its like a skater who spins slowly when his arms are extended
and if he brings his arms close to his body..the spin rate increases '
Ahh!! Enlightenment! Got inspiration!!
After thinking about it..[ it took 1day 16 hours]
after which...
Kungfuhamster was able to explain
"why the Earth rotated when it was made"
Here goes:
Angular momentum is conserved unless
there is an opposite force to counteract the rotation.
That means a spinning object continues spinning.
On Earth, a spinning skater would slow down due to friction.
In space, he would spin forever given
there is no friction in space.
Angular momentum is thus a product
of the spin rate and the moment of inertia
(distribution of mass about the spin axis)
This product is constant in space given
the lack of air to create friction.
The Earth (and other planets) were made
when gases condensed and eventually solidified.
It is unlikely that anything after the big bang would remain still.
All matter would be rotating however slightly.
When gases condense into planets,
the mass is thus distributed more closely
around the axis of rotation.
This amplifies whatever minute rotation there was
initially and thus explains
why almost all planets rotate around its own axis.
Phew! Question answered. What an accomplishment.
Hope you guys understand...
and...hey!!
Take back your laughter...youngling!! (:
Kungfuhamster now has a headache.
Time to sleep...NO!!
cannot got Dnt folio do! SHUCKS!
:D / >.< / ;]
Kungfuhamster is so happy...sittin on Cloud 9
Kungfuhamster just did his EL oral today...
feelin nervous...Kunfuhamster though
he would fail and screw this up
but...
as Kungfuhamster walked into the room
and saw the invigilators...
Kungfuhamster felt overjoyed and elated...
both the invigilators..damn very bloody chio!!
adding to the fact that
they both were young chinese girls
wore very extremely revealing clothes...
you should know what kungfuhamster means
Kungfuhamster now hopes he can strike a
'DISTINCTION' for EL oral examination...
but a 'MERIT' would do just fine...
Well...Kungfuhamster can wait to go church
got wedding...
tommorow got yiss..so please come!!
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